The magician who agrees to come help Micah's mom give birth is pretty shady. For one thing, she doesn't even agree to come until she's promised five silver pieces. And then, she "bit down on each coin to prove the softness and purity of the silver" (3.27) before even going in to help Micah's mom.
She's also kinda gross. When she grabs Micah, telling him to be quiet, he notices "her yellowed fingernails, rimmed in black—little half moons of filth" (1.11). Ick.
The worst thing, of course, is that she lies about Micah's mom being okay, and actually steals everything from the birthing room before leaving. She tells Micah and his dad to let the new mother sleep for a long time—thereby guaranteeing that she'll get away safely with her stolen goods. Ugh. She's not only a charlatan but also a murderer. We can't really blame Micah and his dad for hating all magicians after their experience with this lady.